Problem: If $x \odot y = x-5y$ and $x \bigtriangleup y = xy+4x-y$, find $2 \bigtriangleup (5 \odot 0)$.
Answer: First, find $5 \odot 0$ $ 5 \odot 0 = 5-(5)(0)$ $ \hphantom{5 \odot 0} = 5$ Now, find $2 \bigtriangleup 5$ $ 2 \bigtriangleup 5 = (2)(5)+(4)(2)-5$ $ \hphantom{2 \bigtriangleup 5} = 13$.